how do i know if my cat has fever?

my boy cat had urinary tract problems in the past and since been on special diet for his problem, today threw up and sounding like in agony, his ears feel warmany suggestions, besides taking him to the vet

Try using a digital thermometer. {rectally}A cat's normal temp is 100.5-102.5.

I usually go by how hot their ears or head is. It's suppose to be warm but if it feels like of like you are sticking your hand in front of a heater then he's got a fever. Also, you can use a regular thermometer and stick it under their stomach where they are laying. The normal range is 100.5 and 102.5. It has the same results as a rectal thermometer does. I know people say to feel their nose, but don't go by that! Cats/Dogs noses' are wet due to the fact that they lick them. It doesn't mean they have a fever or not.The best way to tell though is to take him to a vet. He's already been vomiting so he does need to go to rule out any illness. If you can't take your cat to the vet tonight, or anytime soon, and he gets worse you can call your local vets office. If they're not open, an answer machine will tell you the number of a hotline to your vets office to call, when you call that describe what's going on and your vet will call you back asap and determine whether or not you need to bring him in.Good Luck!

And if you don't want to use the rectal thermometer, there are great feline/canine ear thermometers (which I use). If the temperature is over 102.5 by more than a couple points, I'd take your cat to the vet. Fevers need immediate attention and there may be a secondary infection going on.